static int send_config_update_key(const struct sr_dev_inst *sdi,
        uint32_t key, GVariant *var)
{
        struct sr_config *cfg;
        struct sr_datafeed_packet packet;
        struct sr_datafeed_meta meta;
        int ret;

        cfg = sr_config_new(key, var);
        if (!cfg)
                return SR_ERR;

        memset(&meta, 0, sizeof(meta));

        packet.type = SR_DF_META;
        packet.payload = &meta;

        meta.config = g_slist_append(meta.config, cfg);

        ret = sr_session_send(sdi, &packet);
        sr_config_free(cfg);

        return ret;
}


               /* Horizontal increment */
                if (sr_scpi_get_double(sdi->conn, ":WAV:XINC?",
                                &devc->hor_increment) != SR_OK)
                        return SR_ERR;

                send_config_update_key(sdi,
                        SR_CONF_SAMPLERATE,
                        g_variant_new_uint64(  (uint64_t)(round(1.0 / devc->hor_increment)) )
                );